At first glance, pumping concrete into a crawl space may seem logical to homeowners. After all, concrete slabs work well in the garage and basement, and it creates a nice finished look. But sealing and insulation experts say – look again. The cosmetic slab of concrete pumped in a crawl space after new home construction is different than for a basement poured during construction. It is actually worsening the indoor air quality problems it was meant to fix. The result may be the onset of “sick” house syndrome.
The number one reason a homeowner seals a crawl space is simple: it is a wet, musty breeding ground for mold. If left unchecked, mold will migrate upward into a home’s living space and create a costly health hazard. Nasal and sinus congestion, coughing, wheezing, sore throat, headaches, fatigue and eye irritation are among the common symptoms.
Indoor air quality is something you can’t take lightly. There are over 16 million people in the United States who suffer from asthma alone – about 7 million of them children.
The fact is, choosing wet, porous concrete to seal a crawl space is like hiring a wolf to guard the chicken coop. Why? A typical mix contains over 300 lbs. of water per cubic yard of concrete.
A homeowner who agrees to have concrete pumped into a crawl space is unknowingly saturating the entire area with mold-friendly moisture.
And don’t think the environment improves after the concrete dries. In a spacious basement, it is easy for finishers to hard trowel, or close, the concrete surface. But crawl spaces are too small and tight for that technique. So finishers merely top off the poured mass with a hand float. As a result, the slab dries with a chalky finish that disperses dust into the air when scraped by boxes or contractors – or children at play. Unfortunately, the dust contains silica which can cause serious lung damage. So much for the “finished” look.
Installing a vapor barrier – an absolute necessity – before pumping concrete also creates problems. Since the barrier prevents concrete water from seeping into the soil beneath the house, it can only escape upward. That’s a lot of moisture, when you consider that the concrete required for a 1,000 square foot crawl space with a 4-inch slab contains 500 gallons of water (which will be entrapped within the floors and walls of the home).
Also, since concrete does not provide a thermal break, a temperature difference between the air and the concrete surface will cause condensation. And that leads to more mold.
The alternative to pumping concrete is a liner sealing system of the crawl space. The advantages of this solution are many:
- Permanently seals walls and floors.
- Excess moisture is remediated and therefore mold can’t grow.
- Liners stop radon and other natural but deadly gasses from rising and endangering indoor air quality.
- Saves energy costs because the aluminum heat shield reflects warm air into the home, while keeping cold air out.
